1. Field of the Invention
The invention relates to a pulley hub for mounting on a bottom wall of a sheet metal pulley. More particularly, the invention relates to a pulley hub consisting of a pair of tubular members formed of a powder metal mixture which are telescopically joined in a green compact state and then sintered to form an integral homogeneous member which eliminates costly machining operations to provide a hub pulling flange thereon. The invention further relates to an improved method of forming such a sintered pulley hub by pressure and heating steps carried out with a powder metal mixture.
2. Description of the Prior Art
Most pulley hubs are formed from tubular steel stock which is cut to predetermined axial lengths, with the various flanges and grooves being machined or milled therein. These hub constructions are satisfactory for their intended applications, but the machining procedures increase considerably the costs of the hubs. Likewise, removal of metal by machining results in metal waste.
Machining generally is required to form a groove in the hub body which provides a radial annular flange on one end of the hub for gripping by a hub puller for removing the hub and connected pulley from a shaft should replacement be required. Such machining also is required to form flanges and other areas for receiving a sheet metal pulley which is secured thereon by welding, brazing or the like.
Recent years have seen advancements in powder metallurgy and the subsequent production of various hubs from powdered metal by pressing and sintering predetermined quantities and mixtures of such powder metal. Examples of various articles formed from metal powder and methods of producing such articles are illustrated in U.S. Pat. Nos. 2,561,583, 3,260,596, 3,391,444, 3,719,497 and 3,720,512.
Problems, however, have been encountered in attempting to form pulley hubs having pulling flanges formed thereon by powder metallurgy. It is difficult to form an annular groove in the hub body which forms a pulling flange due to the difficulty of press forming such an exterior annular groove in the green-pressed hub compacts prior to sintering by known press molding equipment.
No known pulley hub construction and method of making the same of which I am aware eliminates these difficulties by providing a pulley hub structure and method of forming such a pulley hub having an annular pulling flange thereon, by pressure forming a pair of tubular members in green compact form which, when they are joined and subsequently sintered form an integral homogenous hub with an annular pulling groove and flange.